This research project focuses on pollutants from the combustion of mixtures of dried municipal sewage sludge (MSS) and coal. The objective is to determine the relationship between (1) fraction sludge in the sludge/coal mixture, and (2) combustion conditions on (a) NO(sub x) concentrations in the exhaust, (b) the size segregated fine and ultra-fine particle composition in the exhaust, and (c) the partitioning of toxic metals between vapor and condenses phases, within the process. To this end work is progress using an existing 17kW downflow laboratory combustor, available with coal and sludge feed capabilities. The proposed study will be conducted in concert with an existing ongoing research on toxic metal partitioning mechanisms for very well characterized pulverized coals alone. Both high NO(sub x) and low NO(sub x) combustion conditions will be investigated (unstaged and staged combustion). The proposed work uses existing analytical and experimental facilities and draws on 20 years of research on NO(sub x) and fine particles that has been funded by DOE in this laboratory. For the Fourth Quarter, the authors present an analysis of the data presented in previous reports. These data are on trace metal partitioning obtained from combustion of MSS and Gas, MSS and Coal, and Coal and Gas alone. The results from coal plus municipal sewage sludge combustion suggest a particle size dependence for all three trace elements. This implies that the partitioning mechanixm differs when co-firing MSS with coal than coal alone or MSS combusted with gas assist. This partitioning appears to be surface reaction or pore diffusion related.
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